Sward Condition Research Articles

How does the sward condition in late winter influence the Marandu palisade grass (<i>Urochloa brizantha</i> cv. Marandu) structure during spring and summer?

Height and mowing of a sward in late winter can change its structure during the subsequent spring and summer seasons, which influences plant growth and animal performance. This work was conducted to evaluate the structural characteristics of Urochloa brizantha (syn. Brachiaria brizantha) cv. Marandu (marandu palisadegrass) during spring and summer in relation to the following sward conditions in late winter: short (15 cm), medium (23 cm), tall (31 cm) and tall (31 cm)/mowed to 8 cm. Stages of the grazing period (beginning, middle and end) in spring and summer were considered measures repeated over time. Leaf area index was lower in the tall pasture than in the other pastures and was lower at the beginning than at the end of the grazing period. Dead material mass was highest in the tall pasture, intermediate in the short and medium pastures and lowest in the tall/mowed pasture. Live stem mass was higher at the end than at the beginning and middle of the grazing period of the short, medium and tall/mowed pastures, contrary to that observed in the tall sward. At the end of the grazing period, tiller number did not vary among pastures. The tall pasture in late winter presents a limiting structure to animal consumption. Short and tall/mowed pastures in late winter show a favorable structure for forage plant growth and, probably, animal performance.

Long-term response of an herbaceous sward to reduced grazing pressure and rainfall variability in a semi-arid South African savanna

Reduced grazing pressure is expected to promote recovery of degraded semi-arid savanna. Transformation of degraded livestock ranches to a wildlife reserve in 1982 created a system with about one-third of the grazing pressure, which was maintained until 2011. Herbaceous composition and condition were monitored on four occasions between 1982 and 2011. Baseline measurements were taken following eight years of above-average rainfall conditions. Palatable perennial grasses and sward condition deteriorated markedly in response to severe, sustained drought during the early 1990s. Perennial grasses did not respond to a single record high rainfall season (2000) but recovered following a sequence of four above-average years (2008–2011). This monitoring study illustrated that recovery of a degraded semi-arid savanna may require decades of reduced grazing pressure for some degree of recovery in the absence of intervention. An appropriate time frame for management of these systems is in the order of a century.

Effect of sward condition on metabolic endocrinology during the early postpartum period in primiparous grazing dairy cows and its association with productive and reproductive performance

The effect of different sward herbage allowances and a total mixed ration (TMR) management on milk production, body condition, first postpartum ovulation and endocrine/metabolic parameters were investigated. Primiparous Holstein dairy cows (n=44) were randomly assigned to one of the following grazing treatments (n=11 each): high (HA, 30kg), medium (MA, 15kg) and low (LA, 7.5kg) estimated grass DM available/cow/d and a TMR group fed ad-lib from calving to 56 days after calving. Body condition score (BCS) was registered every 15 days from one month before to two months after calving. Non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), cholesterol, plasma protein, albumin, urea, insulin, insulin like growth factor-I (IGF-I) and leptin were determined in plasma every 15 days from 15 days before to 56 days after calving. Progesterone was determined 2 times per week after parturition to determine first ovulation. TMR group had higher milk production in the first 56 days in milk than the HA and MA groups (P<0.05) which did not differ, and were in turn greater than LA cows (P<0.01). Overall, the TMR and HA groups had a greater BCS, protein and albumin concentrations than the other groups, suggesting a better energy balance. While HA cows presented a better metabolic status (smaller BCS losses, lower plasma NEFA and greater urea concentrations) than MA cows during the early postpartum period (15–30 days postpartum, dpp, P<0.05), HA cows differed (greater plasma cholesterol, albumin and urea concentrations) from LA cows later on (45–60dpp, P<0.05). Greater plasma insulin and IGF-I concentrations were found in the TMR group (P<0.05), which is consistent with the higher nutrient density offered to this group. The reinitiation of ovarian cyclicity was delayed in MA cows one month after calving when compared to TMR and HA cows (P<0.05), which is consistent with the greater NEFA and lower urea concentrations in this period. The lowest probability of first ovulation throughout the study was observed in LA cows (P<0.05), which was associated with their endocrine and metabolic profile. In conclusion, sward allowance affects metabolic signals which in turn are associated with a different productive and reproductive performance.

Dynamics of sward condition and botanical composition in mixed pastures of marandugrass, forage peanut and tropical kudzu

This study was carried out to evaluate the dynamics of sward condition and botanical composition of a mixed pasture of marandugrass (Brachiaria brizantha cv. Marandu), forage peanut (Arachis pintoi cv. Mandobi) and tropical kudzu (Pueraria phaseoloides), rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight). Sward condition was characterized in each stocking cycle by measuring pre- and post-grazing sward height, forage mass and percentage of bare ground. Botanical composition (grass, forage peanut, tropical kudzu and weeds) was evaluated before each stocking period. Swards under smaller forage allowances presented lower height, forage mass and ground cover. This condition favored the growth of forage peanut, which constituted 21.1, 15.2, 8.4 and 3.8% of forage mass in the last quarter of the experimental period, from the lowest to the highest forage allowance, respectively. Tropical kudzu was sensitive to all forage allowance levels and its percentage in the botanical composition was strongly reduced along the experimental period, especially during the dry season (July to September). Forage peanut cv. Mandobi and marandugrass form a more balanced mixture when pre-grazing sward height is maintained shorter than 45 cm. Tropical kudzu is intolerant to intensive grazing management systems when associated to marandugrass.

Productivity, utilization efficiency and sward targets for mixed pastures of marandugrass, forage peanut and tropical kudzu

This study was carried out to evaluate the productivity and utilization efficiency of a mixed marandugrass (Brachiaria brizantha cv. Marandu), forage peanut (Arachis pintoi cv. Mandobi) and tropical kudzu (Pueraria phaseoloides) pasture, rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight), in order to define sward management targets for these mixtures. In each stocking cycle, dry matter (DM) accumulation rates, defoliation intensity (%), grazing depth (%) and grazed horizon (cm) were evaluated. Sward targets were defined according to the sward condition that best conciliated the grass-legume balance and the equilibrium between forage production and utilization. Pastures submitted to higher forage allowance levels showed higher productivity, but were less efficiently utilized. It was not possible to establish sward management targets for marandugrass-tropical kudzu pastures. For marandugrass-forage peanut pastures the best sward state was set with forage allowance of 10.3% of live weight. Under rotational stocking, the following sward targets were suggested for these pastures in the Western Amazon: pre-grazing height of 30-35 cm (June to September) or 45-50 cm (October to May) and post-grazing sward height of 20-25 cm (June to September) or 25-30 cm (October to May).

Land-use, environment, and their impact on butterfly populations in a mountainous pastoral landscape: individual species distribution and abundance

Butterflies were studied, at the species level, in 47 mountain meadows in a 1.5 × 1.6 km study area in the Picos de Europa National Park, Spain. Butterfly transects were carried out on nine occasions in June and July 2004 and the summed data used in binary logistic and stepwise multiple regression analyses using 28 biotic and abiotic parameters. Models were created for 37 species in total: 24 using logistic regression and 24 with multiple regression; models from both approaches were obtained for 11 species. Abiotic factors dominated many analyses with factors such as proximity to water, aspect and altitude being prominent. Abiotic factors may reflect acceptable minimum conditions for presence of a species and interact with biotic factors to determine habitat quality. Classification of the meadows as either under hay or summer grazing management, or ‘winter grazing or abandoned’ was not particularly revealing probably due to inherent variability in management intensity within meadows and degree of abandonment. Features that reflected management influences, lack of management, disturbance, and sward condition featured in many analyses. Whilst many meadows are still actively managed, features that can be related to abandonment are evident for many species. The early stages of relaxation of management intensity can be positive for butterflies, but if management is not restored losses are likely as succession proceeds. The implications of this are briefly discussed.

Influence of sward condition on leaf tissue turnover in tall fescue and tall wheatgrass swards under continuous grazing

SummaryTwo experiments were carried out on a tall fescue sward in two periods of spring 1994 and on a tall wheatgrass sward in autumn 2001 and spring 2003 to analyse the effect of sward surface height on herbage mass, leaf area index and leaf tissue flows under continuous grazing. The experiment on tall fescue was conducted without the application of fertilizer and the experiment with tall wheatgrass received 20 kg P ha−1 and a total of 100 kg N ha−1 in two equal dressings applied in March (autumn) and end of July (mid‐winter).Growth and senescence rates per unit area increased with increasing sward surface height of swards of both species. Maximum estimated lamina growth rates were 28 and 23 kg DM ha−1 d−1 for the tall fescue in early and late spring, respectively, and 25 and 36 kg DM ha−1 d−1 for tall wheatgrass in autumn and spring respectively. In the tall fescue sward, predicted average proportions of the current growth that were lost to senescence in early and late spring were around 0·40 for the sward surface heights of 30–80 mm, and increased to around 0·60 for sward surface heights over 130 mm. In the tall wheatgrass sward the corresponding values during spring increased from around 0·40 to 0·70 for sward surface heights between 80 and 130 mm. During autumn, senescence losses exceeded growth at sward surface heights above 90 mm. These results show the low efficiency of extensively managed grazing systems when compared with the high‐input systems based on perennial ryegrass.

Grazing management strategies for massaigrass-forage peanut pastures: 1. dynamics of sward condition and botanical composition

This study was carried out from October 2002 to December 2003 to evaluate the dynamics of sward condition and botanical composition of a mixed massaigrass (Panicum maximum x P. infestum, cv. Massai) and forage peanut (Arachis pintoi Ac 01) pasture, intermittently stocked at three daily herbage allowance levels (9.0, 14.5 and 18.4% live weight). Sward condition was characterized in each grazing cycle in terms of the pre and post-grazing sward height, forage mass and percentage of bare ground. Botanical composition (grass, legume and weeds) was evaluated before each grazing period. Sward height and forage mass increased linearly with increasing herbage allowance (HA) levels, and higher values were observed during the rainy season. Percentage of bare ground increased primarily at the lowest HA level. Percentage of forage peanut increased throughout the experimental period, primarily in the barest and shortest swards, under the lowest HA level. In the last quarter of 2003 the legume constituted 23.5, 10.6 and 6.4% of the pasture forage mass, respectively, from the lowest to the highest HA level. These results suggest that forage peanut can be successfully associated with massaigrass, as long as the pre-grazing sward height is maintained shorter than 65-70 cm, which will prevent excessive shading to the legume.

Grazing management strategies for massaigrass-forage peanut pastures: 3. definition of sward targets and carrying capacity

This study was carried out to define sward management targets for mixed Massaigrass (Panicum maximum x P. infestum, cv. Massai) and forage peanut (Arachis pintoi Ac 01) pastures in the Western Brazilian Amazon. Seasonal variation in the pasture carrying capacity was also analyzed. Pastures were intermittently stocked at three daily herbage allowance levels (9.0, 14.5 and 18.4% of live weight) from October 2002 to December 2003. Sward targets were defined in terms of the sward condition that best conciliated the grass-legume balance, the maintenance of the structure of Massaigrass tussocks and the equilibrium between forage production and utilization. For the Western Brazilian Amazon conditions, the following sward management targets can be recommended for mixed Massaigrass and forage peanut pastures under intermittent stocking: pre-grazing height ranging from 50-55 cm (June to September) to 65-70 cm (October to May), and post-grazing height from 30-35 cm (June to September) to 35-40 cm (October to May). Annual carrying capacity of this mixed pasture in 2003 was 2.7 AU/ha. The average carrying capacity during the dry season (1.8 AU/ha) was 50% lower than that observed during the rainy season (3.6 AU/ha).

Pattern of herbage intake rate and bite dimensions of rotationally grazed dairy cows as sward height declines

To allow improved prediction of daily herbage intake of dairy cows in rotational grazing systems, intake behaviour was assessed throughout the day in 24‐h paddocks. Herbage intake in 16 lactating Holstein–Friesian cows was assessed using the short‐term (1‐h) weight gain method at four predetermined natural meal times throughout the day (early morning, T1; late morning, T2; mid‐afternoon, T3; and early evening, T4). The study comprised two 4‐day experiments, each with a cross‐over design of four blocks. In both experiments, cows grazed a 24‐h paddock daily, and the effect of the immediately previous grazing experience on intake behaviour was investigated throughout the day, taking account of daily fluctuations in the short‐term physiological condition of the cows. Experiment 1 was carried out to investigate overall grazing behaviour during meals as a sward is progressively depleted during the day, with intake being assessed within the paddock and, hence, on a depleted sward. Experiment 2 similarly investigated the effect of sward depletion and physiological condition throughout the day on intake, but cows were removed to fresh, undefoliated swards during intake measurement periods; thus, intake rate was not influenced by differences in sward condition. Intake behaviour from both experiments was compared to establish the effect on herbage intake of changes in sward state and non‐sward factors. In Experiment 1, sward surface height, available herbage mass, proportion of leaf and green leaf mass declined as the day progressed. Bite mass declined with sward depletion, and mean intake rate was 1·64 kg dry matter (DM) h–1, which was significantly lower at T3 (P &lt; 0·01) than during other meals. In Experiment 2, plot sward conditions did not change throughout the day, and intake behaviour also remained constant, with a mean intake rate of 2·11 kg DM h–1. Mean bite depth as a proportion of pregrazing extended tiller height was constant throughout the day (mean 0·32). The results show that, although cows grazed throughout the day on progressively depleted swards, indicative of rotationally grazed paddocks (Experiment 1), bite mass declined linearly and intake behaviour was variable. However, where intake was assessed on high‐quality, undefoliated swards (Experiment 2), intake behaviour was similar regardless of the time of day and the immediately previous experience. There was some indication of an interaction between the effects of the sward and the physiological condition of the animal on herbage intake.

Impact of sustained drought on a semi‐arid Colophospermum mopane savanna

Vegetation change on different substrate types was measured over 15 years in semi‐arid Mopani Veld. Baseline data were collected in the terminal year (1982) of a decade of above‐average rainfall, whilst the period of monitoring was characterised by below‐average rainfall, with severe drought years occurring in 1988/1989 and 1991/1992. Grazing pressure was, on average, alleviated over the period of recording so that changes reflect primarily the effect of rainfall. Long‐lived perennial grasses had declined markedly, annual and micro‐perennial grasses had increased markedly, and the proportion of forbs had increased. Despite 7–17 years since the replacement of livestock grazing with wildlife at lower stocking rates, there was no evidence of an improvement in sward or soil condition, owing ostensibly to the effect of drought. The extent of change in botanical composition and in sward condition was influenced by substrate type. The rate of growth of the woody component had been slow: the average per annum increase in the radius of trees was 0.67 mm. For the dominant species, Colophospermum mopane, only individuals of less than 1 m in height consistently showed an increase in size. The basal area of dead standing trees had increased threefold. Complete mortality or substantial topkill of shrub species, in particular of Grewia spp., Ximenia americana, and Combretum apiculatum, and of adults of the latter, had occurred owing to drought. Shrub mortality was most pronounced on colluvial soils and sandveld. All species exhibited partial dieback of the crown. Overall, shrub recruitment has been limited except for that of H. mopane on colluvial soils but not on other substrate types, which is therefore likely to increase further its dominance on this substrate at the expense of species richness. Grazing pressure on desirable perennial grasses and browsing pressure on palatable woody plants has probably increased because of their decline, even if animal abundance has not increased, which will have a negative effect on their re‐establishment. Acting in opposition, dieback of trees and shrubs has probably created a window of opportunity for the recovery of perennial grasses, but it would likely require an extended run of above‐average years to reverse the changes in herbaceous vegetation, for which the availability of seed of perennial grasses is likely to be a major constraint.

Draught Requirement of Trailing-foot and Shallow Injection Equipment for Applying Slurry to Grassland

Surface spreading of slurry leads to the inevitable emission of ammonia into the environment. Injection of slurry on grassland reduces these emissions. However, injection of slurry by deep working injector tines with goose foot chisels (wings) requires high draught forces. This type of injection has the risk of the crop dying back under dry soil conditions and is not possible on all soil types. In recent years, new slurry application techniques for grassland have been developed that achieve a large reduction in emissions of ammonia, but require less draught force. These techniques include cutting a shallow slit in the sward, into which slurry is applied, and application of the slurry in bands on the soil surface using a trailing foot implement. In a series of experiments on sandy loam, clay and peat soils, the draught force requirement of single elements of five new slurry application techniques was investigated. The application techniques were a trailed sliding foot element and four shallow injection elements: angled-disc coulters (double-disc opener), thick-disc coulter, flat disc coulter followed by a vertical injection coulter and knife coulter followed by a vertical injection coulter. The application technique, working depth and soil conditions had a significant influence on the draught force. For a working depth of 5 cm, the required draught forces per shallow injector element, measured in this experiment, were in the range of 202–706 N for a double-disc opener, 284–991 N for a thick-disc coulter, 361–1260 N for a flat-disc coulter plus injector and 389–1358 N for a knife coulter plus injector. The lowest draught forces occurred on peat soil and the highest forces on dry clay. The trailing foot required an average draught force of 39 N. The draught force of the trailing foot did not relate to the soil conditions but an effect of the grass sward condition was suggested.

The influence of sward condition on rates of herbage growth and senescence in mixed swards under continuous stocking management

AbstractA study was conducted to determine the influence of herbage mass under continuous stocking management with sheep on rates of herbage growth (G), senescence (S) and net production of green herbage (NP) in a mixed‐species sward of Lolium perenne. Poa annua and Trifolium repens. Plots were maintained in as nearly constant herbage mass as possible at 500, 700, 1000 and 1700 kg organic matter (OM) ha−1 by continuous but variable stocking with sheep for the period May to July inclusive. Estimates of G, S and NP were obtained for each species from repeated measurements over two 2‐week periods on individually identified grass tillers or clover stolons. Estimates of species population densities enabled estimates of G. S and NP per unit area to be made.Rates of G were higher and of S were lower for Lolium tillers and Trifolium stolons than for Poa tillers. The laminae of Poa tillers occupied inferior positions in the canopy of the swards maintained at higher herbage masses and were less accessible to the grazing animals, so that Poa tissue was less well utilized.The total population densities of tillers and stolons declined at herbage masses both above and below 700 kg OM ha−1. The rate of G for the three species combined increased with herbage

Studies on Productivity in Orchardgrass : IV. Varietal differences in dry matter production in sward condition

Studies on Productivity in Orchardgrass : IV. Varietal differences in dry matter production in sward condition

UPLAND GRASS PRODUCTION IN NORTH‐EAST SCOTLAND IN RELATION TO SOIL AND SITE CONDITIONS

An experiment involving 24 grassland sites was carried out to measure the influence of a large number of variables on upland yields between 900 and 1450 ft above sea level in western Aberdeenshire. The grass was harvested in mid‐July and at the end of October 1966. Few factors were significant in the first harvest yields. In the second harvest yields, aspect and soil parent material were both significant at the 1% level, and available soil phosphate at the 5% level. Total yields (DM) for the growing season were correlated with parent material (2% level), with available soil P (1% level) and with the P and K content of the leaf (1% and 5% levels). Yields were also correlated with sward age (5% level) and sward condition (1% level). A number of variables were highly correlated with sward age and condition, including the leaf content (second harvest) of K, P and crude protein (0.1%, 1% and 1% levels).The highest yield was 4700 kg/ha/year and the average yield 2585 kg/ha/year, but the results showed that the average could be substantially increased by good management, especially by P fertilizer. The results confirmed that there was no marked fall‐off in yields with increasing altitude (r=0.066, 0.194 and 0.112) and there appeared scope for reclamation on suitable sites at higher elevations.

Studies on Method of Selection for Snow Resistance and Yielding Ability in Italian Ryegrass Breeding : I. Comparison of Yield and Agronomic Traits between Spaced Planting and Sward Condition

Studies on Method of Selection for Snow Resistance and Yielding Ability in Italian Ryegrass Breeding : I. Comparison of Yield and Agronomic Traits between Spaced Planting and Sward Condition

The regrowth of swards of S24 perennial rye-grass subjected to different pretreatments

In an experiment in which plots of S24 perennial rye-grass grown at a 2 in. spacing were subjected to pretreatments involving two different nitrogen levels and three different cutting frequencies it was found that subsequent regrowth was most strongly related to total stubble weight. Other significant correlations were obtained with root weight, tiller number and weight of water-soluble carbohydrates in roots and stubble.The relationships between cultural treatments and sward condition, and between sward condition and regrowth are discussed in the light of the results from this and other experiments.

The production and utilization of winter grass

The investigations that have been in progress at the Grassland Research Station, Stratford-on-Avon, on the management of grassland for the production of winter pasturage are discussed as four experiments, E 62, E117, E 86 and E158.Exp. E 62 was concerned solely with herbage production, while the remaining three have taken into account the performance of the beef animal under such pasture treatment.The maintenance of condition in the animal has proved possible over a number of winter seasons from 1948 to 1953, sufficiently so to warrant investigation of the means of providing as abundant pasturage as possible at this time of year from latesummer and autumn rested swards. The importance of integrating a system of winter utilization with summer production has become evident in the course of the work, and the necessity of upkeeping sward condition, more especially the grass-legume balance, has been realized. The use of alternate drills of grass and lucerne shows considerable promise in this respect. Intensive utilization and production has taken place from such seedings at all seasons without serious sward deterioration.The development of a grazing system for outwintering cattle destined to be fattened on summer pastures would provide a means whereby such cattle would be fed with as little attention and labour demand as is consistent with good stock management. With the need for cheapening of costs in beef production methods in Britain attention might well be paid to the methods outlined in the light of the experimental data presented.